Configure a health monitor in Cloud Load Balancers

Rackspace's Cloud Load Balancers service includes a health monitoring operation
that helps keep your load balancer operating smoothly by routing traffic only to
nodes that are functioning properly. You set the service by updating the load
balancer configuration settings to add one health monitor per load balancer.
After configuration, the monitor periodically checks the health of each node
associated with the load balancer, including new nodes that you add. If the
health monitor detects an unresponsive node, the system removes it from
the load balancer rotation until the health monitor determines that the node is
functional.

Configure a health monitor

1. Log in to the Cloud Control Panel.

2. In the top navigation bar, click Select a Product > Rackspace Cloud.

3. Select Networking > Load Balancers.

4. Click the gear icon next to the load balancer name, and select Edit Health
   Monitoring.

5. In the pop-up dialog box, select a Monitor Type:

   • CONNECT: The Connect health monitor connects to each node on its
     defined port to ensure that the service is listening correctly. The
     Connect monitor is the most basic health check and does no
     post-processing or protocol-specific health checks. Required information
     for this monitor includes the following details:

     
     • Interval: Minimum number of seconds to wait before executing the
       health monitor. Must be between 1 and 3600.
     • Timeout: Maximum number of seconds to wait for a connection to be
       established before timing out. Must be between 1 and 300.
     • Attempts: Number of permissible monitor failures before removing a
       node from rotation. Must be between 1 and 10.

   • HTTP: The HTTP health monitor is more intelligent than the Connect
     monitor. It can process an HTTP response to determine the actual
     condition of a node. Provide the required information for this monitor.

     

     • Interval: Minimum number of seconds to wait before executing the
       health monitor. Must be between 1 and 3600.

     • Timeout: Maximum number of seconds to wait for a connection to be
       established before timing out. Must be between 1 and 300.

     • Attempts: Number of permissible monitor failures before removing a
       node from rotation. Must be between 1 and 10.

     • HTTP Path: The HTTP path for the sample request.

     • Status Regex: A regular expression used to evaluate
       the HTTP status code returned in the response. For example, you
       could use the regular expression ^(500|40[1348])$ to look for
       unsuccessful status codes (500, 401, 403, 404, and 408) returned
       in the response, or you could use the regular expression
       ^[2][0][02]$ to look for successful status codes of 200 and 202
       in the response.

     • Body Regex: A regular expression used to evaluate the
       contents of the body of the response. For example, you could use the
       regular expression ^.*(Unauthorized|Forbidden|Not Found|Timeout|Server Error).*$ to look for any of those potentially
       problematic strings in the body of the response, or you could use
       the regular expression ^success$ to look for the string success.

       Note: The system evaluates only the first 2048 bytes of the
       response against the body regex you specify, so you should test
       accordingly.

6. Click Save Monitoring Settings to apply your changes.

7. To debug the HTTP health monitoring, test the body regex against the IP
   address of the nodes that you disabled. You can use the following cURL
   command to see what the health monitoring analyzes:

   $ curl -s -r 0-2048 https://YOUR_IP_ADDRESS | head -c 2048 | egrep "YOUR_REGULAR_EXPRESSION"
   

Disable a health monitor

Use the following steps to disable a health monitor:

1. Click the gear icon next to the load balancer you want to update, then
   select Edit Health Monitoring.
2. In the health monitor form, click Disable.
3. Click Disable Health Monitor to apply the change.